Method for the production of the ammonium nitrate component of an nh4no3-containing explosive of high detonation speed

ABSTRACT

THE AMMONIUM NITRATE COMPONENT OF AN OIL- AND NH4N03-CONTAINING EXPLOSIVE OF HIGH DETONATION SPEED IS MANUFACTURED FROM AN INADEQUATELY POROUS COMMERCIAL FORM OF AMMONIUM NITRATE BY GRINDING THE LATTER, SEPARATING FROM THE GROUND MATERIAL THE FRACTION HAVING A PARTICLE SIZE OF FROM 0.05 TO 0.125 MM., COMPRESSING THIS FRACTION INTO A MASS HAVING AN &#34;OPEN POROSITY&#34; OF AT LEAST 10% BY WEIGHT, COMMINUTING THE RESULTANT POROUS MASS, AND SEPARATING OUT THE FRACTION HAVING A PARTICLE SIZE OF FROM 0.5 TO 2MM. THE LATTER IS SUBSEQUENTLY HALFFILLED BY IMPREGNATION WITH OIL SUCH AS DIESEL OIL OR SPINDLE OIL.

United States Patent 3,558,749 METHOD FOR THE PRODUCTION OF THE AMMONIUMNITRATE COMPONENT OF AN NH NO -CONTAININ G EXPLOSIVE OF HIGH DETONATIONSPEED Viktor Rank, Linz (Danube), Hans Tentschert, Leonding, near Linz(Danube), and Harald Junker and Kurt Allgeuer, Linz (Danube), Austria,assiguors to Osterreicbische Stickstofiwerke Aktiengesellschaft, Linz,Austria N0 Drawing. Original application Jan. 30, 1967, Ser. No. 7612,308. Divided and this application July 5, 1968, Ser.

No. 742,703 Claims priority, application Austria, Feb. 2, 1966, A 927/66Int. Cl. C06b 1/04 US. Cl. 2643 1 Claim ABSTRACT OF THE DISCLOSURE Theammonium nitrate component of an oiland NH NO -containing explosive ofhigh detonation speed is manufactured from an inadequately porouscommercial form of ammonium nitrate by grinding the latter, separatingfrom the ground material the fraction having a particle size of from0.05 to 0.125 mm., compressing this fraction into a mass having an openporosity of at least 10% by weight, comminuting the resultant porousmass, and separating out the fraction having a particle size of from 0.5to 2 mm. The latter is subsequently halffilled by impregnation with oilsuch as diesel oil or spindle oil.

The present application is a division of copending application, Ser. No.612,308, filed Jan. 30, 1967, now abandoned.

The invention relates to a method for the manufacture of the NH NO-containing component of an ammonium nitrate-containing explosive ofhigh detonation speed.

It is known to manufacture explosives for industrial application,especially rock explosives, by admixing solid and/ or liquid carboncarriers with solid ammonium nitrate, and at the same time it ispossible to affect the se nsitivity and detonation speed or explosivepower of such mixtures by certain pre-treatments of the ammonium nitrateand/or by further additives. Thus for example attempts have been made toimpart higher porosity to the cheaper, non-porous, dense prill, beforeor after adding carbon-containing admixture or impregnating substances,by grinding, compressing and subsequent breaking-up, in order to improvethe absorptive capacity for the liquid additives. Iun this way it hasalready proved possible to achieve relatively good detonation speeds. Atemperature fluctuation treatment of the ammonium nitrate is alsosupposed to improve the absorptive capacity for liquid carbon carriersby loosening the lattice as a result of changing its structure.

Though several of the methods indicated have achieved good success, ithas now been found that they can be still further significantly improvedby following the procedure described hereinafter. What has been found isthat by suitably selecting the particle size of the starting materialwhich has been comminuted by grinding or crushing, such as crystallineor prilled ammonium nitrate, an increase in the absorptive capacity forliquid carbonaceous fillers beyond the extent hitherto attained can beachieved, without the impregnation oil seeping out on storage.

According to the present invention the fraction of the ground materialhaving a particle size from 0.05 to 0.125 mm. is sieved out for theabove purpose. This fraction Patented Jan. 26, 1971 is condensed bypressure, in any desired manner, into a mass having a porosity,expressed as the oil uptake without leaving a residue, of at least 10%by Weight, and the material is then comminuted into particles having asize of 0.5 to 2 mm. and impregnated with a liquid carbonaceous filler,for example, spindle oil or diesel oil.

Thus in accordance with the present invention there is provided anammonium nitrate-containing explosive of high detonation speed whichcomprises ammonium nitrate having an open porosity, as hereinbeforedefined, of at least 10% by weight, impregnated with a nonexplosive,liquid carbonaceous filler in an amount which stoichiometricallycorresponds to the desired oxygen balance in the explosive.

The high open porosity of the ammonium nitrate produced in the mannerdescribed above is the prerequisite for achieving a detonation speedwhich is significantly increased relative to the normal standard,inasmuch as according to a further characteristic of the invention thesieved and comminuted compressed material is not completely impregnatedwith oil, i.e. until the open pore space is entirely filled, but ratherit is only impregnated with such a quantity of a liquid, non-explosivecarbonaceous filler, such as diesel oil or spindle oil asstoichiometrically corresponds to the desired oxygen balance of theexplosive. Preferably an amount of 5.5 to 6% by weight of thecarbonaceous filler, e.g. oil, suffices for this purpose. A larger orsmaller amount of oil would, in use, result in an undesired excessiveevolution of carbon monoxide or of nitrogen oxide. As a result of theditfer ence between the open pore space and the oil-filled pore spacethere remains, after impregnation, a certain proportion of pores filledwith air which is decisive for the particularly rapid propagation of thereaction wave in the explosive column.

If these two features of the invention, explained above, are observed,namely producing a certain above-normal open porosity in the ammoniumnitrate granules and a partial oil impregnation, detonation speeds of atleast 3000 m./ sec. are achieved, which can even be increased up to 3500m./sec. In order to achieve this high detonation speed it is notnecessary either to add absorptive substances or other explosives.

The ammonium nitrate-oil explosive of high detonation speed of theinvention is thus primarily characterized by consisting of ammoniumnitrate of open porosity of approximately 10% by weight and above andonly such quantity of a liquid, non-explosive, carbonaceous carrier,such as diesel oil or spindle oil as is necessary to set up the desiredoxygen balance of the explosive, preferably 5.5 to 6% by weight. Thehigh open porosity of the ammonium nitrate component which according tothe invention is required for such an explosive is obtained frominadequately porous commercial forms of ammonium nitrate by grinding,compressing, comminution and sieving.

Thus, a characteristic feature of the invention is the process for themanufacture of the ammonium nitrate component of the above-describedexplosive which comprises grinding, compressing and comminuting thestarting ammonium nitrate, sieving from the resulting ground ammoniumnitrate the fraction having a particle size from 0.05 to 0.125 mm.,condensing this fraction into a mass having a porosity of at least 10%by weight, comminuting the said mass and sieving out from the comminutedmaterial the fraction having a particle size from 0.5 to 2 mm.

The following examples illustrate the invention:

EXAMPLE 1 Dense ammonium nitrate prill containing 0.14% by weight ofwater and having an oil absorptive capacity which after immersing theprill in diesel oil and allowing it to drain for 6 hours proves to be3.4% by weight, and

having a bulk density of 0.95 kg./l., was ground in a laboratory mill.The fraction having a particle size from 0.05 to 0.125 mm. was sievedout and compressed in a tablet press, at a pressure of around 200kg./cm. into tablets of approximately 1.5 to 2 mm. thickness. Thesetablets were subsequently broken into fragments of size between 0.5 to 2mm. The ammonium nitrate granules so obtained had high storage stabilityand abrasion resistance. They had an oil absorption capacity of 11.2% byweight in the pores. This oil absorption capacity was determined bypouring oil over the granules in vacuo, separating them from the oilafter releasing the vacuum, and cleaning externally adhering oil off thegranules by means of absorptive paper.

110 g. of spindle oil was sprayed over 2 kg. of these granules andthoroughly admixed therewith, and the product was then placed in an irontube (1 m. long, cm; internal diameter, 5 mm. wall thickness, with ascrew cap at one end) and caused to detonate by means of a primer charge(1 cartridge of gelatine-Donarit). The detonation speed was measured bythe DAutriche method and proved to be 2,900 m./sec. at a distance of 20cm. from the primer charge and 3,300 m./sec. at a distance of 80 cm.

EXAMPLE 2 Dense ammonium nitrate prills were ground as in EX- ample 1.The sieve fraction having a particle size from 0.05 to 0.125 mm. was fedinto a roller press and compressed into sheets at such a high rollerpressure as to result in an internal porosity (determined by oil absorp-I of this ammonium nitrate-oil mixture were introduced into a 3 m. longiron tube of 5 cm. internal diameter and 5 cm. wall thickness anddetonated with a gelatine- Donarit cartridge. The detonation speedsmeasured at 20, and 280 cm. distance were 2,850, 3,350 and 3,400m./sec., respectively.

What is claimed is: t

1. A method for the manufacture of the ammonium nitrate component of anammonium nitrate and oil containing explosive of high detonation speed,said explosive containing 5.5 to 6% by weight of oil, from aninadequately porous commercial form of ammonium nitrate which comprisesgrinding the said commercial ammonium nitrate, sieving from theresulting ground ammonium nitrate the fraction having a particle sizefrom 0.05 to 0.125 mm., compressing this fraction into a mass having aporosity of at least 10% by weight, comminuting the said porous mass andsieving out from the comminuted material the fraction having a particlesize from 0.5 to 2 mm.

References Cited UNITED STATES PATENTS 2,499,321 2/1950 Lyte 149112X3,061,488 10/1962 Scott 149112X 3,095,335 6/1963 McCloud et a1. 149-112X3,111,437 11/1963 Hino et al 149112X 3,305,414 2/1967 Hodgson 149463,453,155 7/1969 Sheeran et a1. 149--112X BENJAMIN R. PADGETT, PrimaryExaminer S. I. LECHERT, ]R., Assistant Examiner US. Cl. X.R.

